I have always used rather large execution squads, since I declined to use men who were specialists for shots in the neck (Genickschussspezialisten). Each squad shot for about one hour and was then replaced. The persons who still had to be shot were assembled near the place of the execution, and were guarded by members of those squads, which at the moment did not take part in the executions.

Quoted in "The Eichmann Kommandos" - Page 157 - by Michael Angelo Musmanno